Combined effects of plasma von Willebrand factor and platelet measures on the risk of incident venous thromboembolism.

Plasma von Willebrand factor (VWF) and platelet reactivity are risk factors for venous thromboembolism (VTE), and VWF can promote hemostasis by interaction with platelets. In this study, we explored the combined effects of plasma VWF and platelet measures on the risk of incident VTE. A population-based nested case-control study with 403 cases and 816 controls was derived from the Tromsø Study. VWF, platelet count and mean platelet volume (MPV) were measured in blood samples drawn at baseline. Odds ratios (ORs) with 95% confidence intervals (CIs) for VTE were estimated across VWF tertiles, within predefined MPV (<8.5, 8.5-9.5, and ≥9.5 fL) and platelet count (<230, 230-299, and ≥300 ×109/L) strata. Here, participants with VWF levels in the highest tertile and with MPV ≥9.5 fL had an OR of 1.98 (95% CI, 1.17-3.36) for VTE compared with those in the lowest VWF tertile and with MPV <8.5 fL in the age- and sex-adjusted model. In the joint exposure group, 48% (95% CI, 15-96) of VTEs were attributable to the biological interaction between VWF and MPV. Similarly, individuals with VWF in the highest tertile and platelet count ≥300 × 109/L had an OR of 2.91 (95% CI, 1.49-5.67) compared with those with VWF in the lowest tertile and platelet count <230 × 109/L, and 39% (95% CI, -2 to 97) of VTEs in the joint exposure group were explained by the interaction. Our results suggest that platelet reactivity and platelet count interact biologically with high plasma VWF, resulting in an increased risk for incident VTE.